[en] The second cancers incidence is increased by 6 to 8 (respectively for radiotherapy and chemotherapy) after one therapy but the increase of incidence after the association of two treatments is up to 19 times higher. Some variations are to noticed according to the treatment: the radiotherapy is responsible of the totality of thyroid and brain cancers. The chemotherapy is responsible of secondary leukaemia but the effect of radiotherapy is to be studied thoroughly. The incidence of secondary osteosarcomas, soft tissues and breast cancers and melanomas is the same after radiotherapy or chemotherapy, the association of the two treatment is responsible of the most of secondary sarcomas. (N.C.)